<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            border:1px solid #000000;
        }
        #contentDiv{
            width: 1000px;
            height: 500px;
            display: flex;/*设置flex布局*/
            flex-direction:column;/*设置子元素排列方向*/
            justify-content: center;
            justify-content: center;        /*space-between;两端对齐*/
                                            /*flex-end;居右对齐*/
                                            /*center;元素居中对齐*/
            align-items: center;
        }
        #contentDiv div{
            width: 100px;
            height: 80px;
            background-color: red;
        }
    </style>
</head>
<body>
    <div id="contentDiv">
        <div></div>
        <div></div>
        <div></div>
        <div></div>
        <div></div>
    </div>

</body>
</html>